Airplane engine ice indicator



Aug 10, 1948 K. E. RoLLEFsoN AIRPLANE ENGINE ICE INDICATOR 2Sheets-Sheet l Filed April 13, 1944A l 1 l I l l I l J Aug- 10, 1948 K.E. RoLLEFsor 2,446,885

AIRPLANE ENGINE ICE INDICATOR Filed April 13, 1944 2 Sheets-Sheet 2 m13450 3E g /g/G/g. ,121

Jag M 105 160 INVENTOR.

and

Patented Aug. 10, 1948 AIRPLANE ENGINE ICE 4INDICATOR Karl E. Rollefson,Evanston, Ill.,`assinor to The Mater Company, Chicago, Ill., acorporation of Illinois Application April 13, 1944, Serial No. 530,892

5 Claims. (C1. 177-311) This invention relates to an airplane engine iceindicator, and more particularly to a device which will give a warningorindication to the airplane pilot of the presence of ice in thecarburetor air induction system of the airplane motor. It is well-knownthat ice forms readily in the carburetor air induction system of anairplane engine to such an extent -that in a. short period of time itaccumulates to a sufllcient degree to constitute a real hazard to thecontinued operation of the engine.

An object of the invention is, accordingly, t provide an indicatorcontrolled by the .air induction system of an airplane motor to give awarning to the pilot of theformation of ice in the carburetor airind-uction system in ample time to permit the pilot to take appropriatemeasures to prevent further accumulation of ice to the point where theperformance of the engine is materially affected.

The invention contemplates the provision of a control system or deviceparticularly adapted for incorporation in the carburetor air inductionsystem of an airplane engine to indicate to the pilot the condition ofthe air induction system in respect to the formation of ice therein,and/or to operate, or initiate operation of, means to eliminate the icefrom the system.

Other and further objects and advantages of the invention will beapparent from the following description when taken in connection withthe accompanying drawing, wherein- Figure 1 is a fragmentary,diagrammatic view in side elevation of an airplane engine embodying theinvention;

Figure 2 is a fragmentary, diagrammatic view in rear elevation takenalong the line 2-2 of Figure 1;

Figure 3 is an enlarged, fragmentary view in vertical section takensubstantially along the line 3-3 of Figure 1; y

Figure 4 is an enlarged view in vertical section of a photocell assemblyforming part of the present invention;

Figure 5 is a view in vertical section of the lamp assembly forming partof the invention;

Figure 6 is a schematic diagram of the photocell indicator, controlcircuit forming part of the present invention.

The atmospheric conditions under which ice may be formed in thecarburetor induction system vary greatly, and extensive research hasshown the impossibility of preventing, by design of the parts of thesystem, the forming of ice under all of those widely varying atmosphericconditions. As is well known, the forming of ice in the air inductionsystem of an airplane engine is one of the most frequent causes of lossof motive power and of motor failure.

The induction system of an airplane engine consists usually of a scoop,an induction carburetor, and a carburetor adapter which connects thecarburetor to a supercharger or to the intake system of the engine. Icemay be formed in the induction system by three different processes. Whensleet, snow, subcooled liquid droplets, or supersaturated air arepresent in the atmosphere, their impingement against surfaces that areat temperatures below 32 F., causes the formation of ice on thosesurfaces. This ice is known as impact ice and usually collects on ornear a surface which changes the direction of the air flow, so thatthe,water or ice particles, with a density much greater than the air arecarried to the surface with a velocity relative to the air screen. Thisice is/usually heaviest on the surfaces of the air scoop above thecarburetor or upon a screen positioned between the carburetor and thescoop. Ice also is formed in or driven `down into the carburetor or thecarburetor adapter, restricting the passages in these devices andreducing the flow ofair and gas to the motor. The most dangerous impactice is that which collects on the metering elements of the carburetor,affecting the fuel-air ratio.

Throttle ice is that whichis usually formed at or near the throttle whenthe outside air temperatures are slightly above freezing and therelative humidity is high, or when the motor is operated with thethrottlein a partially closed position. Because of the increase inenergy of the air flowing past a partially closed throttle, moist airpassing through the carburetor is thereby cooled to the extent that theWater or water vapor condenses and freezes on the surfaces of thecarburetor at or near the throttle. Because of the low capacity of thethrottle temperature drop in cooling the metal parts, the maximumtemperature at which throttle ice is formed is usually about 37 F. Iceforms in the central part of the air stream at carburetor temperaturesabove 37 F., but the metal temperatures are then usually too great forthe ice to collect on the metal.

As the fuel passes through the induction carburetor system it evaporatesafter it is introduced into the air stream and induces a cooling effect,which causes the moisture in the air to condense and freeze on the wallor the walls of the air stream. This is the most common form of icesince it occurs most frequently in actual operation, and because it isformed at carburetor temperatures considerably above 32 F. Most of theheat necessary to evaporate the fuel is supplied from the air as itdrops in temperature during the process of evaporating the fuel. Fuelevaporation ice may ailect air flow by blocking oil or seriouslyrestricting the size of the blower throat; may affect the fuel-air ratio`by interfering with the new of the fuel; and affect mixturedistribution or the quantity of mixture to individual cylinders byupsettingthe fuel flow distribution at the fuel nozzle distributor or byupsetting the air now distribution in the blower throat.

Ice formed under one or any combination of these conditions maymaterially reduce the engine performance or cause engine failure. An icedetecting and/or control system must neceslsarily give accurateindication or accurately affect a control upon the formation of ice any'where in the carburetor induction system, whether such ice is impactice, throttle ice, or fuel evaporation ice, or any combination of theseat a time prior to the accumulation of ice toan,

extent suillcient to affect materially the engine 4 directly or by ascoop adapter casting to the carburetor 30, in turn mounted on thecarburetor adapter l. The carburetor adapter I comprises a hollow elbowcasting having a frusto-l conical elbow surface 32 diverging in anupward direction from a semi-cylindrical elbow surface I4 and merginginto a substantially cylindrical surface 36. The carburetor adaptercasting may be formed integrally with diametrically opposed mountingbosses 3l and i0 for the l'lamp or other light source assembly 2 and thethe surface of each opening extends into the performance. or beforesuchice has accumulated to a sufficient extent that the ice removingsystem of theengine cannot remove the ice before the engine performanceis materially enacted or the engine rendered inoperative. Applicant hasdiscovered vthat surfaces may be provided on which ice may be formed andaccumulate to a sumcient extent to operate the indicator control beforeice of any type has been formed on any part of the carburetor inductionsystem to a sufficient extent to constitute a hazard to the properperformance and operation of the engine. At the same time the indicatoror control is soconstituted that it will not give an indication of thepresence of ice and affect a control operable to eliminate the icebefore a real need exists for removal of the ice, as otherwise therewould 'be unnecessary losses in power and decreases inengine power bythe unnecessary operation of the ice removing system.

'As shownin the drawings, a preferred form of ice indicating control4system embodying the invention may 'comprise a lamp or light sourceassembly zffand' a photoelectric lamp or light sensitive cell assembly 4mounted upon carburetor adapter S ofthe carburetor air induction system8, the carburetor adapter being mounted on the casing section it of theairplane engine I2; an electrically operable lead device, such as anindicator lamp or meter it mounted on the instrument panel I6; anamplier unit it which may be mounted in any convenient position as, forexample. on the rear of the instrument panel Il; and a battery or otherelectric current supply unit 20,- which may be the usual low voltagebattery carried by the airplane.

l'The' carburetor air induction system 8 may comprise the usual meansfor supplying fuel and "air in the proper ratios to the enginecylinders,

such, for example, as air scoop 22 of properly streamlined formprojecting slightly above the usual cowling 24 and facing the propeller26, so that air may be forced into the scoop through its mouth 2l.y Theair scoop may be connected path of the air or fuel mixture passingthrough the carburetor adapter. Applicant has discovered that theseopenings l2 and M so located form chambers in which ice will formwhenever conditions of relative humidity and temperature are such thatice, whether impact, throttle, or fuel evaporation, forms anywhere inthe carburetor air induction system. Hence, the amount of ice in thesechambers at any instant indicates the icing conditions of all Darts ofthe. air induction system or the condition' of icing which will bereached unless appropriate incasel ures are taken to prevent theaccumulation'of ice. 'I

The lamp assembly 2 comprises a lamp Il r'e-s ceived in a socket Il,having supply terminals Il: y and mounted in the transverse endwall-of:er ,z cylinder 62 having an annularilange EC' receivlntl 'y y fasteningmeans. as bolts 8B, by means of which? tlsie cylinder is secured to thehousingcylinder Terminal pins i0, whichl proiectfromathefrrear' of thecylinder 52, are carried byl aninimlatingfA disk E2 fitted into thecylinder B2. 'a spacing-diskbil 54 being interposed between the=disk2fand the end wail of the cylinder b2 and being provided` withlongitudinal openings receiving thepins- 8B* and springs 66 formingresilient means establish--l ing electrical connection between the pinsIl and the terminals 5l).

An externally threaded sleeve t8 forms a i'lt'- ting to which the lampsupply cable 'Ill may be' attached and-forms a housing for the pins Ilwhich may be received'in the usual openingsof the attachingplugcarriedat the end of the cable 10. This sleeve 88 is formed with a mountlnflange 'i2 receiving bolts it, by means of which it is secured to thecylinder 52. A sealing gasket 'i6 is interposed between the mountingflange 121 andthe cylinder 52. A sealing gasket 18 may also beinterposed between the ange 54 of the cylinder 52 and the end of thecylindrical housing 58. The cylindrical housing 58 is formed with amounting flange t0 having a plurality of open-l ings as 82 receivingbolts 84 for fastening the housing to the boss 38 of the carburetoradapter casting 6, and having other openings receiving screws 86, bymeans of which the lamp housing is fastened to a lens housing 08.

The lens housing 88 comprises a cylinder hav` ing an external flangeapertured to receive the screws 86 and being of external dimension tofit snugly in an opening 90 in the boss IB and concentric with thechamber formed by the opens ing 42. y

A pair of condensing lenses 92 and 84 are mounted in the lens housing 86by means of a ring 88, cushioning and sealing washers 8 8 and |88 beinginterposed between the inner lens 82 and the end of the cylindrical lamphousing 58 and between the outer lens 84 and a shoulder formed by theinternal flange |02 of the lens housing cylinder 88.

The lenses 82 and 84 convert the rays from the lamp 48 into a parallelbeam of light projected through the opening 42 transversely of the pathof the air -or air and fuel mixture. This parallel beam of light passesthrough the opening 44 into the photoelectric cell assembly 4.

The lamp 46 may be of the type providing light, rich in infra-red rays,and an infra-red filter may be incorporated in the optical system of thelamp assembly, wherein the sensitivity of the ice detector is such thatthe power of infra-red rays to penetrate vapor mist and to be absorbedby ice or slush to a greater degree than other rays may be usefullyemployed. Thus, for example, where the ice detector is too sensitive tothe presence of a semi-transparent mist when an ordinary lamp isemployed, an infra-red ray lamp may be employed as the source of light,and an infra-red filter may be fitted over the lenses, as, for example,by being set into the end of the lens housing.

The photoelectric or light sensitive assembly 4 may comprise aphotoelectric or light sensitive cell or tube |04 resting upon acushioning pad |06 in a cylindrical housing |08, the housing beingclosed at one end and having bores ||0 and ||2 forming, respectively,the passage for the light beam and an opening for receiving thephotocell. The bore ||2 has an enlarged part forming a shoulder, uponwhich is seated the usual insulated socket ||4. which receives theprongs of the photocell in electrically conducting sleeves (not shown),mounted in the socket and connected electrically to other electricallyconducting sleeves ||'6, which receive the prongs I i8 carried in aninsulating disk |20 fitted in a metal disk |22 fastened as by bolts |24to an integral flange of the housing |08. f

The prongs ||8 project into an externally threaded sleeve |2| whichreceive a companion fitting of a shielded cable |26 and a plug on theend of the cable which has openings to receive the terminal prongs ||6.The cylindrical housing |08 is formed with an annular flange |28 havinga set of openings |30 which receive bolts |82, by means of which thehousing is attached to the boss 40 of the carburetor adapter casting 8,and having other openings receiving screws |84, by means of which lenshousing |36 is secured to the housing |08.

The lens housing |36 comprises a cylinder having an apertured, externalflange receiving the screws |34, and an annular flange |38 forming aseat for a condensing lens |40 held therein by a lens mounting ring |42fitted in the cylindrical barrel of the housing |36. A cushioning' andsealing washer |44 is interposed between the lens and the flange |88,and a similar washer |46 is interposed 'between thellens mounting ringand the end of the cylindrical barrel of the housing 6 photoelectriccell may be of the type having maximum sensitivity to infra-red rays.4The ,lens |40 concentrates the beam of light onthe light sensitivesurface of the photocell.

The photoelectric cell |04 is connected by the cable |26 (Figures l to3)v to the direct current amplifier unit AI8, to which the lamp 46 isconthe cable |26; the wires |56 andv |60| represent the cable |52; thewires |62 and |64 represent the cable |50; and wires |66 and |68represent the p cable 10. Within the amplifier unit the wire |54,

|68, which is fltted ln the cylindrical barrel of the i lens housing 36.The cylindrical barrel of the lens housing |36 snugly fits into anopening |48 in the boss 40 and concentric to the recess 44.

An infra-red ray filter between appropriate washer rings may besubstituted for the washer |48 to exclude rays other than the infra-redrays from the photoelectric cell housing, in which the which extendsfrom the anode |10 of the photoelectric cell, is connected by wire |12to the control grid |14 of a beam power amplifier tube |18v having, inaddition to the control grid, a filament |18, a cathode |80, a screengrid |82, beam forming plates |84, and an anode plate |86.

The anode i|10 of the photocell is also connected by the wire |54 to oneend of a resistor |88 connected at its opposite end through a supplywire to one terminal of a switch |82, the other terminal of which isconnectedto the wire |62 of the cable from the battery 20. 'I'he otherwire |64 of the battery cable is connected directly to a supply wire|84. The supply wire |80 constitutes the positive side of the circuitand the supply wire |84 the negative side of the circuit. The cathode|86 of the photoelectric cell is connected directly by the wire |56 tothe negative supply wire |84. Filament |16 of tube |16 is connected onone side by wire |96 to the negative supply wire |84, and by wires 200and 202 to a resistor 204, in turn connected to the positive supply wire|80. The cathode |60 is connected by wire 208 to the self-biasingresistor 208 connected, in turn, to the negative supply wire |84. Thecathode is also connected by wire 2|0 to the control grid 2|2 of asecond beam power amplifier tube 2 |4 having filament 2|6, cathode 2 I8,control grid 2 I2, screen grid 220, beam forming plates 222, and anodeplate 224. The anode |66 of the tube |16 is connected directly by thewire 226 to the positive supply wire |80, and the screen grid V| 82 isconnected to the anode by wire 228. The beam forming plates |64 are, ofcourse, connected to the cathode |80.

Filament 2|6 of the tube 2|4 is connected in parallel to the filament|18 of the tube |16 by wire 230 and wire 232. The cathode 2|8 Aof tube2|4 is connected by wire 234 to one end of the resistor or resistorsection 236, which in turn is connected in series with a resistor orresistor section 238 and across the supply wires |80 and |84 as by wires240 and 242. The anode 224 of the tube 2|4 is connected by wire 244 toone end of the coil 246 of a relay 248, the other end of the coil 246being connected by wire 250 to the positive supply wire |80. Relay 246includes a switch 252, the movable blade of which is connected directlyto the wire |58, and the fixed contact of which is-connected as by wirel254 to the positive supply wire.

'I'he lamp 46 is connected by the wire |66 to one end of a resistor 256,the other end of which is connected directly to the supply wire |80, and

the wire |68 is connected directly to the supply assassin 3 J thebattery `20 through the wire 92. the switch |02, the voltage droppingresistor 2te, the wire |00, the lamp 48, the wire Hi8, the wire i04, andthe wire |64. When the light from the lamp 48 falls on the photocell, acurrent ows from the positive supply wire |90 through resistor 80B, wire|04, photocell |04, and the wire |58 to the negative supply wire |94.The voltage applied to the control grid |14 by the photoelectric cellmaintains the current iiowing from the positive supply wire |90 throughwire 223, the anode itt, cathode |00, and the resistor 208 to thenegative supply wire |94 at such a minimum value that the voitage dropacross the resistor zilt is not sumcient to overcome the negative biasapplied by the selfbiasing resistor 23B, and, therefore, does not permitsuiliclent current to flow through the coil 246 of the relay 248 toactuate the relay. Hence the switch 252 remains opened and the signallamp I4 extinguished.

When, by an accumulation of ice, slush, or frost in the chambers formedby the openings 42 and 44, the light passed to the photoelectric cell isreduced by a certain extent, the voltage applied to the control grid|14, relative to the cathode |00, is so varied that the consequentcurrent through the resistor 20B creates a sufficient voltage dropacross the resistor to overcome the negative bias of the grid 2|2, andconsequently the plate current of the tube 2 i4, which flows through therelay coil 246, is increased sufiiciently -to effect closure of theswitch 252. Hence, the signal lamp I4 is energized and provides a visualindication of the icing conditions in the air induction system. Thepilot will thus be warned by the lighting of the lamp |4 thatappropriate measures should be taken to eliminate the ice in thecarburetorv induction system or to prevent'further formation of ice inthe system.

- It will be evident that in place of, or in addition to, the lamp I4 anammeter may be substituted in the plate cathode circuit of the tube 2|4to provide a constant indication, by the position of the meter needle,of the icing conditions in. the carburetor induction system, so that thekpilot'can know at any instant how much, in a relative sense, ice hasaccumulated in the carburetor induction system.

The chambers formed by the openings 42 and 44 are of: the utmostimportance in the proper operation of the ice detector, for theyprovide, as applicant has discovered, a place for ice to form before iceforms anywhere else in the carburetor induction system, and ice willform or accumulate in these openings prior to its accumulation anywhereelse in the system, whether that ice being formed ,is impact ice,throttle ice, or fuel evaporation ice.

It will be evident that the relay 240 may itself initiate and terminateoperation of any known de-icer or heater means for eliminating the icein the induction system.

Changes may be made in the form, construction, and arrangement of theparts without departing from the spirit of the invention or sacriilcingany of its attendant advantages, and the right is hereby reserved tomake all such changes as fairly fall within the scopeof the followingclaims.

What I claim is:

1. In a carburetor air induction system, means providing a wall iurfacedefining a passage for air and air-fuel m xtures, means forming achamber set into said surface and communicating with said passage, meansfor projecting a beam of rays through said chamber, a ray sensitivemeans communicating with said chamber to receive light passing throughthe chamber, said chamber being constructed and arranged to provide aspace in which ice forms and accumulates prior to its formation anywhereelse in the system under all icing conditions, and a load deviceactuated by said ray sensitive means upon accumulation of a given amountof ice in said chamber.

2. In a fuel supply system for an airplane engine, pipe means adapted tobe connected to the fuel supply system for receiving the air fuelmixtures and adapted .to transmit the air fuel mixtures to the engine,said pipe means having oppositely disposed openings therein, a lamphousing mounted on said pipe means, a lamp in said housing aligned withone of said openings, lenses in said housing aligned with said oneopening for projecting the light from said lamp as a parallel beamthrough said one opening and across the air-fuel transmitting passage ofsaid pipe means, a photoelectric cell housing mounted on said pipemeans, a lphotoelectric cell in said last mentioned housing in alignmentwith the other of said openings, a lens housing mountedonsaid pipemeans. and a lens in said housing positioned to direct the rays oi saidparallel beam of light received through said other opening onto saidphotoelectric cell, said openings providing recesses for theaccumulation of ice in the path .of the light beam.

3. In a fuel supply system for an airplane engine, a hollow fittingdirecting the fuel mixture to the engine, said fitting having internalangularly related surfaces defining a passage converging in thedirection of movement of the fuel mixture, an aperture through saidfitting laterally of said passage and opening into said passage. at theintersection of said surfaces to provide a chamber in which ice formsprior to its formation elsewhere in the system, means for projecting abeam of light into said chamber, a photoelectic cell mounted to receivethe beam of light from said chamber under the control of ice in saidchamber. and means controlled by the photoelectric cell and constructedand arranged to indicate the presence of ice in said chamber in anamount indicative of such icing conditions within the system as toconstitute a hazard if not removed. N

, 4. In a carburetor air induction system, an arrangement foranticipating the formation of ice in any air passage of said systemcomprising a carburetor adapter having a passage through which airpasses, the wall of the passage having lates prior to its accumulationin said passage, a

ray source and a ray sensitive means constructed and arranged to sensethe presence of ice in said recess, and a load device actuated by saidray sensitive means upon detection of ice by said ray sensitive means.

5. In a carburetor air induction system, means for detecting theincipient formation of ice in said system comprising means providing asurface upon which ice forms from the air and air-fuel mixtures in saidsystem and a recess extending inwardly from said surface and at itsinner end ush with the surface to provide a space in which -iceaccumulates prior to its accumulation on said surface, a ray source andray sensitive means so positioned in relation to said recess that theice forming in said recess controls the transmission of rays from` thesource of said ray sensitive Number Name Date 10 means, and a.load-device actuated by said ray Number Name Date sensitive meansuponaccumulation of ice ony said 1,785,392 Sawford et al. Dec. 16, 1930surface. 2,212,211 Pfund Aug. 20, 1940 KARL E. ROLLEFSON. 2,280,400Green Apr. 21, 1942 l 2,338,574 Cunningham Jan. 4, 1944 REFERENCES CITED2,355,014 Schorn Aug. 1, 1944 The following references are of record inthe 21371259 Patterson Mar- 13; 1945 me of this patent: p OTHERREFERENCES UNITED STATES PATENTS y. 1 Publication, LAerotecnica, Aug.1939.

Publication, Electronics Feb. 1932, page 61,

878,456 Darwin Feb 4 1908 Article and gule, Robot Humide.

Certificate of Correction 'Patent No. 2,446,885. August 10, 1948.

KARL E. ROLLEFSON' It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionas follows: AColumn 8, line 75, claim 5, for the. words of said" read tosaid; and that the said Letters Patent should be read with thisgirection, therein that the same may conform to the record of the easein the Patent Signed Aand sealed this 30th day of November, A. D. 1948.

THOMAS F. MURPHY,

Assistant Oommzaeioner af Patents.

